John's Model Making

Sunday, November 18, 2018

I plan to continue to update this "blog" post so there will be a single place where you can go to find most of the details (or at least links to other posts in the series).

Tormach Envy

I've had a Taig CNC mill for over 10 years. This has been a really great machine and has worked well for making small injection molds. About a year ago, I upgraded it to ball screws, which has given it new life (the backlash with the lead screws was getting pretty bad). I documented that upgrade here:

However, recently I've been having a serious case of Tormach envy. I've had my eye on a PCNC 770, and now 770M mill. This provides a little larger work area than my Taig, as well as other features. But there is a huge price difference. I purchased my Taig for about $2,000 (would be about $3,000 today). Whereas the 770M is about $15,000 for what I would want. That's a huge difference.

So let's take a look at what I found so compelling about the Tormach that I don't have today with my Taig.

More powerful spindle

Spindle on/off and speed control

A little more Y movement

TTS

Power draw bar

Haimer or ITTP

Fogbuster

PathPilot

Before I got into the details, there is one major thing that kept me from buying a Tormach. We're currently in a rental house while we wait for our new house to be ready, and I don't have room for a Tormach right now. This has kept me from taking the plunge. But while talking with Kevin, another hobby CNC machinist at work, he mentioned that Tormach has had serious problems with backlash. After doing a bunch of research, I came to the conclusion that this seems to impact a very small number of machines, and seems to be a result of poorly scraped ways. You can find more in this post: Facebook Post. And also in my video below:

So after a bunch of research, I learned that there are other upgrades for the Taig for the spindle motor, the frame, and the spindle. Once I'm done with these upgrades, I'll have most of what I wanted in a Tormach, but for a lower price (less than $2,200 for the upgrades). Sounds compelling, right? Let's take a closer look.

Specs Comparison

Movement

Machine

X

Y

Z

Taig

12"

5.5"

6"

PCNC 440

10"

6.25"

10"

PCNC 770

14"

7.5"

13.25"

Note: I can add a .75" extension for Y on the Taig, providing a total of 6.25" travel.

Spindle

Taig: 1/4 hp

PCNC 440: 3/4 hp

PCNC 770: 1 hp

770M 1.5 hp

So in many respects, the 440 is pretty close to what I would get from upgrading my Taig. Therefore, I looked at the price of a new 440 with PathPilot and a power drawbar (but no enclose, base, TTS sets, etc. so it would be a better comparison). The total came out to $7,850.

On the other hand, the Taig upgrades (new frame, TTS spindle, power draw bar, new spindle motor) come to about $2,150. This of course, is using my existing 5019CNC mill ($3,000 today) and computer. If you factored in a cheap computer and stepper controller and you started from scratch, it would probably cost about $5,000. That's still an extra $2,800 for a 440. That's probably worth it if you just want to make chips. But if you're willing to do some work, you can get a nice machine for less money.

PCNC 440: $7,850.90

PCNC 440 Base Machine: $5,995

PathPilot Controller: $795

Power Drawbar: $695

Standard LCD monitor: $195.50

Keyboard, jog shuttle, etc.: $169.40

Taig: $5,145

Taig 5019CNC: $2,995

Consew motor, pulleys and belt: $150

Frame upgrade: $500

TTS spindle & power drawbar: $1,500

Spindle Upgrade

The stock spindle motor on the Taig is a 1/4 hp motor, whereas the Tormach PCNC 770 has a 1 hp motor, and the 770M has a 1.5 hp. That's a pretty big difference. The Tormach also has spindle speed and on/off under software control. Whereas, on my Taig, I have to flip the switch for on/off control, and change pulleys to change speeds. The pulleys give me 6 different speeds, from 1,050 to 10,600 RPM.

After doing some research, I stumbled upon the Taig Lathe And Mill Owners Club on Facebook. This is a pretty active community, and finally got me onto using Facebook. There I learned about a very inexpensive motor upgrade using a sewing machine servo motor. The Consew CSM1000 motor is a 3/4 hp motor, so close enough to the PCNC 770. I purchase one from Amazon for about $100 and some pulleys and a new belt (another $50):

The first motor was defective, so I sent it back and got a replacement that works. For the price, the hassle was OK.

In order to use this new motor, I needed to mill a motor mount, order some pulleys and belt, and the bore out the larger pulley to fit the Consew motor shaft. I found a motor mount in the Facebook group that also had the CAM already set up (but you'll need to use less aggressive feeds with the stock motor):

Sunday, November 4, 2018

Cutter compensation is a great way to dial in a hole to be a very precise size. I learned about cutter compensation from a John Saunders video How to Use Cutter Comp on a Tormach! WW180. In his video, he's using PathPilot on a Tormach. But I have Mach3 with a Taig, so the workflow is a little different. But not by much.

First, some background. Cutter compensation is done use a set of g codes: G41 and G42. Which one to use depends on the direction of cut. Fortunately, Fusion 360 handles choosing the correct one based on what you're trying to do.

Here's the high-level overview of how it works. Normally, Fusion 360 will calculate the correct location of the tool path based on the diameter of the cutter. In the picture below, you can see that it's moved the tool path for the cutter inward by half of the tool diameter.

In other words, Fusion 360 is handling the calculations to compensate for the diameter of the cutter.

Cutter compensation in Fusion 360, at least at the time I'm writing this, is only supported for 2D operations.

Setup in Fusion 360

If you change the default In computer to In control, you're telling Fusion 360 that the controller (Mach3 in my case) will handle compensation instead. Here is how you make that change:

Once you regenerate the tool path, you'll see the following:

This may be a little hard to see, but now the tool path (the blue line) is exactly along the profile, rather than 1/2 a diameter away.

Setup in Mach3

Mach3 has a tool table. I have never used this before, which means I've always been using tool 1. To set a tool diameter in this table:

Edit G Code

You might think you're done, and ready to make small changes to the diameter (making it slightly smaller to make the hole larger). But that's not the case. Fusion 360's post processor for Mach3 emits g code that looks something like this:

G1 G41 X3.11 Y-1.65 P0.125

G3 X3.26 Y-1.5 I0. J0.15

Notice the P0.125 at the end of the line that contains G41. This tells Mach3 to use this tool radius instead of the value in the tool table, so you have to remove this. Additionally, I found comments that Mach3 doesn't like having G41 on the same line as other commands. So, I edited the g code so the above appears like this:

G41

G1 X3.11 Y-1.65

G3 X3.26 Y-1.5 I0. J0.15

Once I made those changes, I was able to slowly change the diameter of the cutter in the Mach3 tool table until I had the hole just the right size. I started with 0.25 and then worked my way down to .244 (I made the hole in CAD slightly smaller than my target).

Thursday, February 9, 2017

I just wanted to post a quick note about a project I've been working on. I have been designing and building a pick and place machine for building electronic circuit boards (also known as PCBs). The tiny electronic parts mostly come in tapes. And I needed a way to hold these tapes firmly in place, and at the same height as the top of the circuit board. As a result, I ended up creating a 3D printed, spring loaded tape holder:

Not long after posting this on the OpenPnP forum, I got an email from the owner of Liteplacer.com asking if I'd be willing to let him make an injection molded version for mass production. Printing the parts you see above takes a few hours. Since I've created quite a few injection molds in the past, I offered to take this on. By the way, here is what a bunch of them look like, waiting for tapes to be added for a job:

This, after a number of iterations, I settled on this design:

From here is was a matter of designing and created the injection molds. I used SolidWorks 2011 to create all of the designs above. However, I decided to try Fusion 360 for designing the molds and creating all of the tool paths for the milling machine. I've been documenting the process with YouTube videos, that you can find here:

This project started when I wanted to learn how to create circuit boards, and I thought it would be nice to have FSRs on my delta printer. When I posted my progress on one of the forums, other forum members started to ask if they could buy one.

I was a little daunted by the prospect of building 50 circuit boards (which later became 100). Fortunately, I have a friend, Dave, who needed some money, and he was more than happy to assemble the circuit boards. I suggested that instead of paying him by the hour, I would let him have the profit. That worked out really well for both of us. But after programming and shipping out 100 boards, I was happy to be done.

(On a side not, I just realized I need to get a photo of the two of us so I can add it to this post. I’ll try to do that soon. We’re both model railroaders, and we work on a friend’s model railroad. His next get-together is October 4, so I’ll try to get a photograph then.)

Some people asked how they could get boards after the run of 100, and someone suggested that I contact one of the companies selling 3D printer products. I contacted Tridprinting.com for several reasons. First, I’d met the owner, Daniel, at a mini Maker Faire in Seattle, and he’s a nice guy. Second, I’ve always had a very good experience ordering supplies from him. And finally, he’s local, so I could meet with him in person and deliver boards in person. He said yes, he would definitely like to sell my circuit board. Cool! But then he told he how many. I was thing a small number and trying to figure out how to keep the price down.

We had sold the first 100 circuit boards direct for $10 each, so there was room for profit after the cost of supplies. I had been ordering these in batches of 50, so didn’t have the best discount. Ordering in larger batches reduces the cost of the parts. As it turned out, however, this was a small part of the total cost, especially for domestic manufacturing.

I contacted several companies here in the Northwest US to get quotes. The quotes were for the blank PCB, the parts, and assembly. Their quotes did not include flashing the program, testing, soldering on header pins, or packing into anti-static bags. I figured my friend Dave could help me with those tasks, until I saw the quotes. I was surprised (or perhaps shocked) at how much they charged for the PCBs as well as for assembly. They also had a pretty hefty setup fee for the circuit boards, and another setup fee for programming the pick-and-place machine. Since this board only has 15 parts on it, I didn’t expect the pick-and-place cost to be as high as it turned out to be. We would have to increase the price quite a bit if we went with domestic manufacturing, at least with the supplies I contacted.

Production in China

I’d been reading good things about Seeed Studio in China for open source hardware, so I contacted them for a quote. I first contacted them at the end of June, and they sent me a spreadsheet to fill out. They had some questions, and got back to me the next day with a quote. And their quote was way below (less than half) the quotes I got here in the US. And their quote include flashing, testing, and packing into anti-static bags. Wow, no wondering people have their products made in China. I wish I had a better option locally, but at the moment I don’t.

I sent Seeed an engineering sample of a built-up circuit board and a blank PCB to help ensure I got what I wanted. For some reason that I don’t remember, it took me until the end of July to send them payment. They required full payment up front, so I was sticking my neck out a little here. During the same time, I worked on a test plan. This was a simple one-page document that I sent them. I described what the circuit board does (what all the pins do), and described how to test the board. And that’s it.

I got an email from them on September 1 saying that they had finished production, and would be sending out the boards. It took about 10 days to get here to the US and through customs. It was held up in customs for a few days, and then arrived here. Yay! Here’s what I got:

Nice, very nice. I’m very happy with the results. They built these quickly, packaged them very nicely, they look great, and they work perfectly. What more could you ask.

Seeed’s Programming and Testing

I was curious about how Seeed went about programming and testing this board, so I asked them if they could provide me more information and photos. They sent me their test plan document, which was in Chinese, so I don’t know what it says. But it did include some photos. First, this is how they programmed the boards. The ISP programmer is connected at the top-right:

Here is a photo that shows the setup they used for testing, which makes use of a couple of Seeed’s circuit boards:

The bottom board is a Seeeduino, which is an Arduino clone, and the FSR circuit board is plugged into the I2C connector in order to receive power. I don’t know what the top-right board is called. However, they made a custom cable, shown below, that allows them to connect the LED to the endstop output of the board. This allows them to test all three FSR inputs to ensure that the light turns on or off when the FSR inputs are shorted.

So they did a nice job with the testing as well. Their solution was very simple, but effective. I don’t think they actually used the Arduino clone for anything other than power, though.

Arduino. I installed Arduino 1.0.5-r2. Even though you won’t be using this directly, you’ll be using the avrdude program included with the installation

Six-Pin Header

Adding the programming header

Solder in either a 2 by 3 pin header, or two rows of 3 pins as shown below. You’ll be connecting the programmer to these pins, and the board will also receive power from the programmer.

Connect the programmer

Plug your programmer into your computer, and then connect the cable between the programmer and the FSR board as shown. Note the direction of the cable coming away from the FSR board

Also notice that the green power-on LED is on once the programmer is attached, as the FSR board receives power from the programmer.

Running avrdude

The final step is to send the new firmware to the board. The instructions below are for Windows. You can find more information about using avrdude here: Starting out with avrdude. First, locate where you have Arduino installed. The avrdude program will be in a folder under that location: hardware\tools\avr\bin\avrdude.exe. Copy this full location.

Open a command prompt and navigate to the location where you’ve downloaded one of the hex files. Then run this command (all on one line):

You’ll want to substitute your actual path to avrdude for the one here, and you’ll want to use the actual name of the hex file. You should see progress information from avrdude while it’s downloading and then verifying the firmware. While the firmware is downloading, the green LED on the FSR board will be dark. It will come back on once the firmware starts running again.

Monday, July 7, 2014

I backed the Kickstarter campaign for the Pegasus Touch SLA printer, which I got for $2,250. At that price, and given the samples they were showing, I thought it might be a good deal. Of course, with Kickstarter, you never know. And I’ve been seeing grumbles on the forum from other people who have received their printers (or perhaps not).

I received my box a few weeks ago and finally had a chance to set it up this past weekend. The packaging was good, and there were no issues with broken parts. The box included the printer, a 1/2 liter bottle of clear resin, and the power supply. That’s it. No manual.

I downloaded the manual and software and setup the machine on my desk. My desk isn’t near an Ethernet jack, so my desktop computer is connected via Wifi. No problem, the manual indicated that I could print without a network connection, using a USB thumb drive. So I fired up the machine. A splash screen appeared, and then the screen went blank after about 10 seconds, and just stayed that way. Even after 10 minutes, it was still blank.

OK, perhaps that meant I needed to update the firmware first. But how to do it. I checked the manual again, and the manual said that “Ethernet is the preferred interface but USB PC connection (requires microUSB cable, not supplied) and WiFi (requires dongle, not supplied) are also supported.” So, I connected the USB cable, and after some fiddling to get the drivers installed properly on Windows, the machine showed up in my devices list. And now RetinaCreate (their software package for talking to the printer) told me that the printer’s firmware needed to be updated. However, I couldn’t find a way to update it.

Finally, I moved the machine to another location where I could plug it into an Ethernet wall jack. It booted, and I was able to update the firmware. It turns out the manual isn’t correct, and you need a hard-wired Ethernet connection, at least to get started. I haven’t tried it without, so I’m not sure what does and doesn’t work. However, I was able to print—yay!

First Print

I loaded a model into RetinaCreate that I’ve been working on for a while to stress test the printer. This is a small caboose in HOn3, and it’s just under 7 cm long. You can find more details in my previous blog posts:

You can click on the image to see a larger version. Below I’ll describe more about what I learned. But first, here is what the 3D model looks like in Solidworks:

And finally, here is what I had in RetinaCreate:

In case you caught that I had clear resin, the picture above is after spray painting the model with light gray, which makes it a lot easier to see what the surface looks like. Also, I hand-modified some of the supports after using the automatic support generation feature.

What I learned

First, I learned that this printer has a lot of potential for creating small models. Until I printed this model, I wasn’t sure it would live up to the task. Sure, the printed part will need some sanding to smooth out the curved surfaces, but so do models from Shapeways.

I also learned a lot about working with SLA printers, which is very different from working with FFF printers. The model is printed upside down, and that meant that uncured resin got trapped in various parts where I didn’t want any resin. As an example, look at the floorboards at the end of the caboose. In the printed model, they didn’t turn out very well. A lot of resin got trapped under (or above when printing) the floorboards, so there was a lot of goopy resin still in there when I took it out of the printer. The floorboards also didn’t cure very well. That may mean I need more support, or it could be a result of the goopy resin above.

As it turns out, the orientation I used was completely wrong. I’d always wondered why SLA printers tended to print parts at strange angles. Well, now I know—it’s to allow the uncured resin to drain out of the part as it prints, so you don’t end up with partially cured goop. Using clear resin probably doesn’t help, as any trapped resin can still receive some light. I really want to get some tinted resin to see what difference that will make, because the laser doesn’t travel very far into opaque resins.

After printing this part, I discovered that RetinaCreate has a button called Find Optimal Rotation that only appears when you have the object selected. I had not noticed that. Here is what it looks like when I use that option:

That’s a very different. I’m not convinced this is the optimal angle, but I’m going to give it a try.

Saturday, July 5, 2014

In my previous post (Building the FSR Circuit Boards) I showed how we assembly our circuit boards, using a manual pick and place machine that I designed and built. You can also find videos on that post. In this post I’ll walk through building the machine.

Building the X/Y Assembly

Start by printing four of the Y Post parts, and then cut two pieces of aluminum tube about 18 inches long. You can make them longer, but I wouldn't go much shorter. A length of 18 inches will give you about 11 inches of movement along the X (left/right).

Next cut two pieces of aluminum tube about 12 inches long (or longer). Using 12 inches will allow movement of about 7 inches along Y. Print two sets of Y Carriage, Bottom Rollers, and Bottom Roller Clamp parts. Use the M8 x 30 bolts and washers to mount the 608 bearings to the Y Carriage. The washers go between the bearings and the part, and the M8 bolts are self-threading. Add the 608 bearings, washers, and bolts to the Bottom Rollers parts.

Place each Y Carriage assembly around one X assembly and then use the Bottom Roller Clamp with some M3 x 20 screws to clamp each Y Carriage assembly to the aluminum tube of the X assembly. This picture should help:

The bottom roller clamps don’t need to be really tight. They’re to keep the top rollers in place when you lean your hand on the carriage.

Now insert the two Y tubes into the holes of the Y Carriage and then mount to a piece of plywood. It's best to screw down one side first, with the screws centered in the slots so you have some room for adjustment. Then attach the other side, ensuring the assembly moves smoothly from left to right.

Building the Pen Holder

Print the Pen Holder and LM8 Cap parts. The 8mm aluminum tube slides through two LM8UU bearings. The tube will need to slide up and down smoothly, as well as rotate. I found I needed to sand the tube down a little to get just the right fit. Do this slowly, testing the fit frequently.

Insert the 8mm tube into the two LM8UU bearings, and then clamp them in place using the LM8 Cap part, held in place by four M3 x 12 screws. At this point you’ll still be able to remove the tube.

Insert two M8 x 50 bolts, as shown through the three holes. Add an M8 nut to the back of each bolt and tighten. Next add one 608 bearing to each bolt, along with an M8 washer, and put it up against the square tube, as shown here:

Add another 608 bearing to each bolt, followed by an M8 nut. Hand tighten each of the three nuts evenly, ensuring that the assembly slides smoothly without any slop.

Building the Pen

Print the Pen to Tube and Spring Stop parts. Add the spring, then the spring stop (which has a slot on the bottom for the spring). Use an M3 x 12 screw to clamp the spring stop in place. Apply some pipe tape to the tapered part of the Pen to Tube part and then push it into the aluminum tube. Finally, push the air hose onto the nib. When you’re finished, it should look like this:

Print out the Lock to Tube Adapter and Pen to Tube parts. Carefully push the Luer adapter into the Lock to Tube Adapter at the larger-diameter end. It should look like this (when you also have a needle in place):

In the photo above, I’ve also added some pipe tape to the tapered part to help create a tight air seal. You’ll want to push this into the tube after the tube is in place. When you’re done, it should look like this:

Optional USB Microscope

I initially installed a USB microscope in order to help with placement, but I found it to be more confusing them helpful. The problem is that it’s looking at the part from an angle, so it’s actually harder to line up parts with the microscope than with your eyes (stereo vision really helps). My friend uses a pair of Optivisors and found they work really well. I’m near-sighted, so I just take off my glasses. But if you do want to install a USB microscope, I purchased this one: